Field of the Invention
The present invention generally relates to a method to prevent the rupturing of a mechanical seal used in centrifugal pumps. More particularly, the present invention relates to a lubrication mechanism for the mechanical seal.
Description of the Related Art
Centrifugal pumps are the most preferred hydrodynamic pumps used in domestic and industrial applications. The centrifugal pumps are provided with mechanical seals that are protective devices specially engineered to be used in the centrifugal pump. The primary function of a mechanical seal is to prevent liquid under pressure from leaking out of the pump and to prevent air from drawing into the pump. The mechanical seal is also used to reduce friction and power losses of the shaft, increase the flexibility to negate the shaft deflections, and to improve the overall reliability of the pump. Hence, the mechanical seal needs to be lubricated or replaced at regular time intervals to prevent it from rupturing.
In current industrial practice, the lubrication process of the centrifugal pump is operated without the use of control systems and thus there is no control on the fluctuating temperature of the lubricant. In some cases when there is no fluid flowing through the pump due to human or technical errors, the pump has to be shut down as it may hamper the life of the pump. The mechanical seal on the centrifugal pump has two metal surfaces in contact with each other. In such conditions, absence of a coolant, such as oil field fluids, or oil as used ordinarily in pump applications, causes the temperature of the mechanical seal to rise. This may cause the mechanical seal to crack; thereby damaging the mechanical seal.
The rise in temperature of the mechanical seal depends on the type of fluid running through the pump, the velocity with which the fluid is running and the impurities it carries along with it among other factors. If the fluid is more concentrated with slurry than water, the temperature of the pump and the mechanical seal rises drastically. Generally, the temperature of the mechanical seal always falls in the range of about 250-300 degree Fahrenheit.
Great Britain Patent No. 1,600,673 discloses a mechanism relating to lubrication of a mechanical seal. Oil housing is placed between a drive unit and a pump unit of a submersible pump. The oil housing contains various chambers filled with oil, which is used for lubricating and cooling the bearings and seal of the pump. However, the invention fails to mention the cooling mechanism of the oil housing. During the operation of the pump if the oil gets heated up, its purpose to be used as a coolant is defeated. Another Great Britain Patent No. 1,241,944 discloses an oil reservoir for lubrication of a mechanical seal used in rotary vacuum pumps.
Another example of an arrangement of the oil chamber around the mechanical seal is shown in Japanese Patent No. 2,014,051,938. The mechanical seal has a seal chamber filled with lubricating oil and is installed in the inner side of the pump. If due to human or technical error, fluid stops flowing through the pump, the seal chamber might get heated up as it is placed on the inner side of the pump. This increases the possibility of rupturing of the seal when the pump is in operation and there is no flow of fluid through the pump.
Chinese Patent No. 202,326,370 discloses an air layer to protect the mechanical seal submersible pumps. Chinese Patent No. 102,032,168 discloses a mechanical sealing device for a pump which effectively prevents the spring from being corroded, and reduces the abrasion of the sealing surfaces.
In another example a U.S. Pat. No. 8,414,257 discloses an improved self-priming centrifugal pump for improving the efficiency of the pump. U.S. Pat. No. 5,322,428 discloses a gear transfer pump with lubrication and sealing of the driveshaft and idler pin and U.S. Pat. No. 8,540,478 discloses architecture of a multi stage high pressure pump. U.S. Pat. No. 4,202,654 discloses a wear resistant self-lubricating centrifugal pump and U.S. Pat. No. 6,422,822 discloses a pressurized seal for submersible pumps. A lubricated shaft seal is disclosed in U.S. Pat. No. 3,762,724 and an improved seal section located between the motor and the pump for equalizing pressure of motor lubricant contained in the motor is disclosed in U.S. Pat. No. 7,665,975.
The above prior art systems and methods suffer from one of or more of disadvantages, including irregular lubricant supply to the pump and the mechanical seal, rupturing of the seal over short periods of time, human and technical errors, and so forth.
The art is replete with patents regarding pumps and improvements thereto. However minimal to no information has been found regarding centrifugal pumps and extending their shelf life by maintaining oil in their system at all times. In light of the foregoing discussion, there exists a need for an innovative lubrication mechanism of the mechanical seal used in centrifugal pumps which maintains the life of the pump by keeping fluids flowing there through when the pump is suddenly and unexpectedly having a loss of fluid flow.